Glass-ceramic restoration of eroded teeth is becoming a routine
therapeutic procedure. The glass-ceramic prosthesis is held in place
by adhesive bonding, the strength of which is dependent on the
materials and specific techniques employed. The clinical case study
presented afforded the opportunity to optimize and fine tune the
bonding procedure. Surface treatments of the different substrates
(tooth and ceramic) have been developed so as to maximize the
strength of the adhesive bond of ceramic to both underlying dentin and
enamel. The success of the procedure is often evaluated by the time
that the prosthesis remains in the oral cavity. This case demonstrates
those three years after bonding, the restoration remains securely in
place despite a severe accident resulting in a root fracture.Keywords: Bonding; Ceramic; Erosion; Adhesion; Occlusion;
Treatment planning

In modern society there is a high and still increasing
prevalence of dental erosion [1-3]. Reported prevalence is
variable in the literature complicated by other forms of tooth
wear, age, country's origin and evaluation standards. Erosive
tooth wear is caused by sustained direct acid attack of enamel, the
acid arising from an intrinsic source such as gastro esophageal
reflux or vomiting or extrinsic sources [4-7]. The extrinsic
causes of dental erosion can be grouped under the headings of
environmental, diet, medications and lifestyle [8]. Glass-ceramic
restoration of teeth to treat dental erosion is becoming a routine
procedure in modern dentistry as it not only enables conventional
treatment but also provides aesthetic improvements over
metal-ceramic restoration [9,10]. Glass ceramic prostheses are
securely bonded to underlying supporting tooth structures with
adhesive cements. The strength of the bonding is paramount
in determining the success of the completed restoration. There
has been a plethora of research examining adhesive bonding in
ceramic restorations and the factors that affect the strength of the
bond [11-16]. Not only is the strength of the bond influenced by
the materials employed but it is also dependent on the procedure.
This case study provided an opportunity to investigate the
bonding of ceramics to dental structures and to further optimize the procedure with respect to the surface treatment of both
substrates (tooth and ceramic).

A 31 year old male patient presented at the clinic due
to �absence of teeth in his smile� nd expressed a wish for
restoration. He had been an inpatient in a psychiatric hospital
for 10 years. He did not complain of pain or masticatory
deficiency. The hard tissue erosion was thought to be a result
of the patient's medication. Anti- depressant and anti-psychotic
medicines often have anti-cholinergic peripheral side effects and
therefore can have an impact on salivary flow and composition
[17,18]. Decreased salivary flow and alterations in the clearance
and buffering capacity of saliva will result in a more acidic
environment in the oral cavity. Demineralization of enamel
occurs if the oral environment reaches a critical threshold of pH
5.5. In addition, due to the symptom of �dry mouth� the patient is
likely to have consumed more beverages potentially exposing the
teeth to acid attack from a dietary source (Figure 1).
Clinical examination revealed a severely eroded dentition
with the anterior maxillary teeth and the premolars most
significantly affected. All teeth were vital and there was no other
clinical symptomatology. The periodontum presented as a thick
biotype with significant attached gingival (Figure 2).
The severity of dental erosion as classified by Vailati and
Belser was deemed to be Class V which indicates extended dentin
exposure on the palatal aspect, loss of the incisal length of the

Figure 1: The smile is contracted but shows dentition.

tooth (> 2mm) together with distinct reduction/loss of facial
enamel [19] (Figures 3 and 4).
The buccal version of the mandibular incisors and the absence
of egression of the maxillary anteriors are due to the interposition
of the tongue. The Vertical Dimension of Occlusion (VDO) did
not appear diminished and the molars adequately interlocked.
The occlusal plane was correct without any deformities or
abnormalities. The intermaxillary relation showed no severe
mandibular protrusion and no lateral deviation in intercuspal
relationships was established during the pre-prosthetic
evaluation. The molars were in a Class I of Angle relation. There
was no anterior guidance because of the erosion. Tooth number
seven was missing and the lateral incisor had been replaced by
a canine during orthodontic treatment 15 years previously. The
centre of the maxillary incisors was laterally positioned.

The primary therapeutic objectives were the rehabilitation of
function and aesthetics. The treatment aimed to respect the teeth
together with the conservation of as much tissue as possible. The
patient wanted to avoid surgery and lengthy orthodontic work
and expressed a wish for the best possible treatment within a
short timeframe.

Prosthetic strategy

A premolar to premolar restoration in the upper and lower
maxilla was proposed. The diagnostic wax up revealed that the
VDO had to be augmented in order to build correct proportions for
the final teeth. (Figure 5) Final restoration was to be performed
in a centric relation and there were to be no major changes in the
occlusal plane.

Figure 2: Frontal view of pre-operative situation.

Figure 3: Frontal view of pre-operative situation.

Figure 4: Occlusal view of the maxilla.

Figure 5: Wax up of the central incisive without VDO augmentation,
normal anatomy cannot be built in that situation.

Figure 6: Wax up of the central incisive without VDO augmentation,
normal anatomy cannot be built in that situation.

The restoration options available to treat and rectify this
case of severe dental erosion are either to look for retention
or to exploit the remaining tooth structures and use adhesive
bonding. The former is the more conventional approach and
involves endodontic treatments, insertion of posts for maxillar
anteriors, and crowns on vital teeth in the posterior region.
Materials can either be all-ceramic or metal-ceramic, although
all-ceramic restorations are preferable to than metal-ceramic as
they have superior aesthetics and are more biocompatible [9,10].
The occlusal concept is commonly a mutually protected occlusion
with canine or group guidance.
The second option represents a more moderate treatment
method, taking advantage of the large enamel band around the
incisors and canines and aiming to conserve as much original tissue and dental structure as possible. Although there was very
little capacity for retention in this case, there was good adhesion
potential. The materials of choice in this approach are glass
ceramics for their bonding ability. Lithium disilicate ceramic
offers a material that has the necessary characteristics of good
mechanical strength combined with the capacity for natural light
transmission [20]. These ceramics are produced with pressed
ingots (Emax Press � Ivoclar Vivadent) and depending on the
restoration thickness they are either stratified (anterior region)
or lightly coated on the posterior region. The occlusal concept
in this scenario is generally a balanced occlusion in order to
minimize lateral impacts on the anterior guidance [21].

explanation of both options, the second approach was chosen,
notably as it seemed preferable to conserve the tissue and
remaining dental structures, and also for the fact that the first
approach remained a viable option in the event of failure of the
latter method.
The second approach is dependent on the adhesive process
and the mechanism and strength of adhesion is very much
influenced by the type of adhesive employed and the technical
procedures and protocols followed. To this end, a review of the
literature revealed that there are many protocols and procedures
employed in glass ceramic bonding and that there was potential
to optimize these procedures in order to achieve a strong
adhesive bond (Figure 5).Treatment plan and clinical stages

A full wax up enabled the evaluation of the proposed
treatment plan and VDO adjustment (Figure 6).

he primary temporary prostheses were made from shells
that were jointed because of the poor retention offered by
the available tooth structures after preparations (Figure
7).

The shells were relined with acrylic resin and luted with
polycarboxylic acid without Eugenol (Durelon) [22]
(Figure 8).

he patient and the practitioner were able to test the new
occlusion and aesthetic for a few weeks, making necessary
adjustments and occlusal equilibrations (Figure 9).

The final restoration began with the molars so that
the occlusal relation was stabilized by premolars and
anteriors. The molars were rebuilt with table-tops, also
called overlays, the most appropriate technique in order
to raise the VDO with a consevative approach [23].

ubsequently the anteriors and premolars were
bonded. Final equilibration was performed following the
technique of Fillastre [24].

The luting session of ceramic prostheses: The process
of adhesion of dental prostheses must not only take into
consideration the nature of the luting agent(s) and the material of
the prostheses but also the techniques and procedures employed
to obtain a strong and long-lasting bond. The literature indicates
that there are different protocols followed in order to maximize
the strength of the bonding [25]. Before sound adhesion can be
obtained it is necessary to prepare and treat the surfaces to be
adhered. This is applicable to any adhesion process and maybe
more so in prosthetic dentistry where the permanence of the
bonding is determinant of treatment success. The two surfaces
involved are the ceramic prosthesis andremainingtooth.Treatment of the tooth side: Isolation with a dental dam
provided control of the dental surface while the temporary
cement was removed with ultrasound followed by pumicing with
a brush so that the tooth surface was adequately cleaned [26,27]
(Figure 10).

Figure 10: The 8 table tops for the molars.

Figure 11: Removal of the temporary cement with ultra sound and
pumice.

Figure 12: Sandblasting to optiminize bonding.

Figure 13: Etching of table tops.

Optimization of the treatment of the tooth surface involved
sandblasting with alumina, 27 µm, 2-5 bars, 10 seconds, in order
to develop the surface energy and enhance the mechanical retention of the adhesive [28] (Figure 11).
The etch and rinse system with a primer then bonding with
4th generation adhesive is still the gold standard in terms of
retention and micro leakage, particularly on to enamel [29].The standard protocol followed encompassed:

Etching enamel for 30 seconds with phosphoric acid at
34% v/v.

Etching dentin for 15 seconds maximum.

Rinsing for 30 seconds.

Light air blasting, no drying.

Application of primer and gentle brushing.

Light air blasting

Application of bonding material, gentle brushing.

Light air blasting to evaporate solvents.

Light curing for 40 seconds.

Materials employed: Syntac™ and Variolink II™ from Ivoclar-
Vivadent.
Treatment of the ceramic side: Surface treatment of
the ceramic prior to bonding is a standard prerequisite. A
fairly standard protocol was initially followed but there were
opportunities where optimization steps were included. Box 1
summarizes the surface treatments for glass ceramic (Figures 12
and 13).The procedure involved:

Etching with hydrofluoric acid (125% concentration during
30 seconds using Porcelain-etch® Ultradent) again in
order develop surface energy and to increase mechanical
adhesion of the resin (Figures 14 and 15). Etching time is
dependent on the concentration of acid used and on the
nature of the glass ceramic as shown in Box 1.

Rinsing for at least 30 seconds.

Drying of the surface with air blasting.

Application of silane : two thin layers on two orthogonal
directions, brushing the surface and allowing to evaporate,
in this case ceramic primer®( 3 M) was used .
Optimization of the procedure comprised heating the silane
to 125oC has this been shown to increase tensile strength of the
bonding. This can be achieved with a hair dryer or better in a
ceramic furnace [30,31], this is the chosen option for this case.
The dual composite (Variolink II™ was injected and the excess
removed with a brush (Box 1)End of luting session: It is important to finish the luting
session by treating the inhibited surface layer with oxygen. Two
methods are available: either a glycerin gel is applied before the
last curing, or a little excess of luting resin will be polished. The
former method was used on this occasion as it seemed more
practical with respect to the excess of resin before the light curing.
Primary occlusion corrections were made followed by
polishing, final occlusion corrections and application of fluoride
varnish on the margins to minimize sensitivity and to fill in
microporosities. The patient was provided with a night mouth
guard to minimize parafunction effects (Figures 16, 17 and 18).

Box 1: Showing etching times and silane treatment of glass-ceramic.

Figure 14: Silane brushed and dried.

Figure 15: Work in progress during the luting session.

Figure 16:Occlusal view of bonded table top before corrections.

Figure 17:Polishing the occlusal correction is mandatory.

Figure 18:Because of the very poor retention on the canines group
fonction on excursions are realized, controlled and polished.

considered successful, a minimum of 5-years preservation in
the oral cavity is necessary, so future evaluation of the same
restoration will validate the applied optimization procedures.
While the conservation of tissue was possible in this case
and was consistent with the initial aims for the treatment, it
also meant that options remain available if future treatment is
required. In the event of failure of the bonding it will still be
possible to either re-bond, re-do the ceramic employing different
materials or utilizing alternative procedures, or to opt for the
more conventional retention option (Figures 19 and 20).

The procedures employed allowed for maximum tissue
conservation and was in agreement with the patient's expectations
in this case. The success of the treatment is dependent among

Figure 19:Occlusal view of the maxilla at the end of the treatment.
Function and esthetics are restored.

Figure 20:Frontal view of anterior arcade at four years recall.

other parameters-on the strength of the adhesion of the glass
ceramic to the dental structures. The tensile strength of this
bonding mechanism is influenced not only by the agents used but
also by the surface treatment of the adhering surfaces and the
techniques employed. Optimization steps have been adopted at
both the surface treatment stages and at the luting stage in order
to maximize bond strength. The permanence of the prostheses is
the definitive measure of treatment success and the recall at four
years gives satisfaction to the patient and the dental team.

Acknowledgement

The authors would like to thank the dental laboratory
Creadent, Grabels, France, for the great technical part of the case.
Authors are grateful to Mss Orla Cassidy for the tremendous help
in the writing of the article. The FLAP is a study group from south
of France, they have to be thanked for their energy and pleasure
in work.